"8·3"日地沟泥石流运动特征及堵溃分析OA

On August 3,2024,a super-large-scale debris flow disaster occurred in Ridi gully,Kangding City,Sichuan Province.The disaster losses were extremely serious,and the blocking and breaching effect within the watershed was remarkable.Based on methods such as field investigation,remote sensing interpretation,and theoretical calculation,this study systematically analyzed the movement characteristics of the debris flow and the characteristics of channel blocking and breaching.The research findings are as follows:By combining with the field slurry preparation test method,the average bulk density of the debris flow is determined to be 2.080 g/cm3,belonging to viscous debris flow.The rainfall intensity of the"August 3"debris flow in Ridi gully is once-in-a-hundred-year.The peak debris flow discharge of the once-in-a-hundred-year event in the entire watershed of Ridi gully is 980.73 m3/s,and the debris flow discharge at section 3-3'(near the gully mouth)of the"August 3"debris flow in Ridi gully is 1828.66 m3/s.The average flow velocity in the section ranges from 6.98 to 7 m/s,and the amount of solid materials flushed out by the debris flow at one time is approximately 568,800 m3.Through remote sensing interpretation and field investigation,10 potential blocking and breaching hazard points are identified in the upper reaches,among which 5 locations have a high recurrence risk.And the D9 blocking and breaching point is the largest in scale and the most harmful.The peak debris flow discharge calculated by the morphological investigation method is 1.86 times that of the once-in-a-hundred-year peak debris flow discharge calculated by the rainfall-runoff method,indicating that the blocking and breaching effect in the middle and upper reaches of Ridi gully is significant.Numerical simulations of debris flows with different recurrence intervals in the Ridi gully are carried out using MassFlow.For the debris flow with a return period of 100 years,the deposition depth of the debris flow is 0-9 meters and the flow velocity is 0-11 m/s.The results show strong agreement with the on-site investigation(the error of the debris fan area is less than 15%),and it will block the main river.Seismic activity and heavy rainfall are the main causes of the"August 3"debris flow.The disaster presents a three-stage chain evolution characteristic of"landslide-collapse-blocking-breaching".The results of this study can provide scientific support for the precise prevention and control of debris flow disasters in the high and steep gully valleys in western Sichuan.